Thursday, 17 March 2016

Search and rescue dogs are commonly used to find people trapped in the debris of collapsed buildings, but are search and rescue rats next? A new study suggests the rodents can be trained to find people and then return to their release point after hearing a signal.

The study was conducted by researchers at Western Michigan University and APOPO, a Belgian nongovernmental organization that has previously trained giant African pouched rats (Cricetomys gambianus) to sniff out landmines and tuberculosis.

Pouched rats have the potential to make even better search and rescue animals than man’s best friend. Dogs can take years to train, are inconvenient to transport, and, because of their size, cannot penetrate rubble but have to search for scent as they move over and around it. Giant African pouched rats, native to sub-Saharan Africa, are agile and climb well. They should have little difficulty moving among debris. Like dogs, they have a keen sense of smell. These rats are relatively inexpensive to house, train, and transport, and unlike dogs, they do not depend on a particular human handler to work well. Pouched rats can live more than eight years in captivity, so early investment in training can pay off over a protracted period. Finally, the rats are large enough (adults have body lengths between 25-45 cm and weigh 1-2 kg) to carry appropriate equipment. In this study, that equipment was a small video camera and a beeper to signal the rat to return to its release point.

For more than 10 years, APOPO has been training pouched rats to sniff out landmines by rewarding them in a series of training stages that increasingly resemble real-world conditions. For the new study, the researchers tested whether the same technique could be used to train rats to find people in collapsed buildings.

The first stage of training was socialization. From three to six weeks of age, the rats were handled by people and exposed to different sights, sounds, and smells as they were hand fed treats like peanuts and bananas. During this time, the rats were also fitted with backpacks that held a miniature video camera and small beeper, to which they readily habituated.

Next, the researchers trained the rats to approach and place their paws on a target person and then return to their starting point at the sound of a beep. Gradually, they increased the distance the rats had to cover and added obstacles that simulated a collapsed building, like damaged wood and furniture. The target people eventually hid beneath and behind the obstacles, requiring the rats to walk through and climb over the debris to contact them. In order to receive their tasty rewards, the rats had to reach the target person and then return to their handler.

The rats were first trained in a 5 x 5 m area. When they reached more than 87 per cent accuracy, they moved on to a larger (6 x 9 m) area that contained even more obstacles. On average, it took the rats 21 sessions to reach 80 per cent or greater accuracy in this larger area.

Then the rats were put to the test. This time the rubble could be hiding a person, a bag containing recently-worn clothing, or an empty bag. Each of the five rats tested located the human target most often and the empty bag least often. Overall, rats found the target within three minutes on 83 per cent of human target trials, 37 per cent of clothing trials, and 11 per cent of empty bag trials, so they seemed to find the challenge of locating humans the easiest of all. Moreover, each rat spent the most time in proximity of the hidden person and the least time near the empty bag.

The researchers say it’s not surprising that pouched rats can be trained to sniff out people; the interesting finding is that both searching for humans and returning on command were easily trained together. Both these behaviors will be necessary if the rats are to be used to search for survivors in collapsed buildings. In a real-life situation, the rat would leave the handler, search for and find a person buried in rubble, and then return to the release point at the signal so the handler could examine the video captured by the rat for signs of survivors.

This study provides proof of principle, but the researchers say a great deal of behavioral research will be needed to produce working search and rescue rats. Even under the simplified testing conditions, the rats sometimes failed to locate the person. Multiple rats searching an area together might be required in real life conditions, as APOPO does with its landmine detecting rats.

Also, if pouched rats are to be useful search and rescue animals, they will have to perform in even more challenging conditions. More research is required to investigate the effects of variables like the presence of dust or smoke, temperature extremes, and a much larger area. The animals might have to wear muzzles to prevent them from eating any food they find, and be taught to continue searching despite the presence of food or other interesting distractions.

And what about some people’s antipathy towards rodents? “Trained pouched rats are friendly and attractive animals, but they are rats nonetheless,” note the authors. They suggest a small light might be included to allow a camera to operate and inform survivors that the rat is a trained search animal and not a wild scavenger. Rats could also carry a reassuring printed message to that effect.

Landmines, tuberculosis, and now people under debris – APOPO is just scratching the surface of what rats can do for humans.

Post written by Mary Bates (@mebwriter) for the BPS Research Digest. Mary Bates is a freelance science writer specialising in the brains and behaviour of humans and other animals. She has been published in National Geographic News, National Geographic's Weird & Wild blog, New Scientist, the Society for Neuroscience's BrainFacts website, plus many other outlets. She earned her PhD from Brown University, where she researched bat echolocation and bullfrog chorusing. You can follow her on Twitter and Facebook and see all of her work at her website.

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